Electrical connection pattern in an electronic panel

ABSTRACT

A connector layout for arranging a plurality of parallel electrical connectors between two electronic devices. In one device, each connector has a strip connected to a bump pad. The bump pad is superimposed on and electrically connected to a bump pad on the other device. Each strip has a certain required strip width and each bump pad has a certain required pad width. The connectors are grouped into a group of three or more. Within each group, a strip is connected to a bump pad along one side edge thereof, and the bump pads are offset in two directions such that after the bump pads are superimposed, the pattern of the connected connectors in each group of connectors resembles a plurality of zigzag paths offset to maintain a constant gap between two strips. As such, the gap between two connectors can be minimized.

This is a continuation-in-part application of and claims priority to aco-pending U.S. patent application Ser. No. 11/198,117, filed Aug. 4,2005, assigned to the assignee of this application.

FIELD OF THE INVENTION

The present invention relates generally to electrical connectionsbetween two devices in an electronic panel and, more specifically, tothe electrical connections between a display device and a drivingdevice.

BACKGROUND OF THE INVENTION

In a display panel comprising a display device and a driving device,electrical connections between the display device and the driving deviceare usually designed to maximize the number of connectors within anavailable real-estate between the two devices. In a liquid crystaldisplay (LCD) panel, for example, a gate driver and a data driver areelectrically connected to an LCD device in order to operate the LCDdevice (see FIG. 1).

A thin-film transistor liquid-crystal display (TFT-LCD) is a type offlat-panel liquid-crystal display (LCD) device composed of an array ofpixels. Each pixel is controlled by a gate line and a data line. Asshown in FIG. 1, the TFT-LCD device 200 is composed of an array ofpixels 210 and is controlled by a data line driver IC 230 and a gateline driver IC 220. In FIG. 1, G₁, G₂, . . . , G_(m) are gate lines andD₁, D₂, . . . , D_(n) are data lines. Preferably, both the driver ICsand the TFT-LCD device are disposed on the same glass substrate. Afterfabricating the TFT-LCD device on the glass substrate, driver ICs aremounted on the substrate via a so-called chip-on-glass (COG) process.Each of the driver ICs and the LCD device has a plurality of connectorsso as to provide the electrical connections between each of the driverICs and the LCD device.

FIG. 2 only shows the electrical connections between the active area ofthe LCD device 200 and a driver IC 220, as established by the COGprocess, for example. As shown in FIG. 2, the connectors on the activearea of the display device 200 include a plurality of conductive stripsegments 332 connected to a plurality of bump pads 330. The bump pads330 are wider than the strip segments 332. As shown in FIG. 2, theconnectors on the driver IC 220 include a plurality of bump pads 340disposed on the underside the driver IC 332. The bump pads 340 arecomplementary to the bump pads 330. When these connectors are connectedtogether to provide electrical connections between the display deviceand the driver IC, each of the bump pads on the driver IC issuperimposed on a corresponding bump pad on the display device.

Referring to FIG. 3, as commonly seen in prior art, bump pads arearranged in a shifted pattern 350 so as to increase the number of bumppads in a unit length while maintaining a suitable distance between thetwo connectors. A typical completed display panel is shown in FIG. 3. Asshown, the display panel 10 has a gate driver IC 220 and a data driverIC 230 electrically connected to active area of the LCD device 200. Thepanel also has a strip of wires-on-glass 270 and a strip ofwires-on-glass 272 separately connecting the gate driver IC 220 and thedata driver IC 230 to a bonding tape 260 so as to provide electricalconnection to a PCB 250 or the like. The shifted pattern 350 of theelectrical connections is shown in detail in FIG. 4.

As shown in FIG. 4, the width of the bump pad is W₁ and the length ofthe bump pad is W₅. A gap W₄ is kept between two adjacent bump pads. Thethickness of the strip segment is W₃. Given a pitch P between twoconnectors, the shortest distance between two connectors is W₂, whichcan be determined as follows:P=W ₂+(W ₁ +W ₃)/2Due to the mechanical tolerance in the bump pad superimposing process,the acceptable smallest gap between two connectors is about 7 μm. IfW₁=23 μm, W₂=7 μm and W₃=5 μm, we have a pitch P=21 μm.

The demand for higher resolutions in display devices heightens therequirement for having more signal channels on a given area of thesubstrate. This means that the pitch should be reduced if possible.However, the width of the bump pad, W₁, should not be further reduced,because the total area of the bump pad, W₁×W₅, should preferably be atleast 2000 μm² to provide a good electrical connection between a bumppad of the IC and a corresponding bump pad of the display device.

Thus, it is advantageous and desirable to improve the bump pad layoutpattern so that the pitch can be reduced without changing the width ofthe bump pads or the width of the strip segments while maintaining theminimum distance W2 between two adjacent connectors.

SUMMARY OF THE INVENTION

The present invention provides an efficient connector layout forarranging a plurality of parallel electrical connectors between twoelectronic devices on an electrical panel. The layout of the connectorson one electronic device is complementary to the layout of theconnectors on the other electronic device. Each connector on one of theelectronic devices has a strip connected to a bump pad. Each strip has acertain required strip width and each bump pad has a certain requiredpad width. Each bump pad on one electronic device is superimposed on acorresponding bump pad on the other device so as to provide electricalconnection between the devices. The present invention connects a stripto a bump pad in a certain way and arranges the bump pads in a certainpattern so that, given a certain pitch, the gap between two connectorscan be minimized. In particular, the connectors are grouped into a groupof three or more. Within each group, a strip is connected to a bump padalong one side edge of the bump pad, and the bump pads are offset in twodirections. After the bump pads are electrically connected bysuperimposition, the pattern of the connected connectors in each groupof connectors resembles a plurality of zigzag paths offset to maintain aconstant gap between two strips.

The present invention will become apparent upon reading the descriptiontaken in conjunction with FIGS. 5-13.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will become apparent from a consideration of the subsequentdetailed description presented in connection with accompanying drawings,in which:

FIG. 1 is a schematic representation of an LCD panel having an LCDdevice connected to a gate driver IC and a data driver IC;

FIG. 2 is a schematic representation of the electrical connectors,according to prior art;

FIG. 3 shows a typical finished LCD panel with a prior-art bump padlayout;

FIG. 4 shows the various dimensions in a prior art bump pad layout;

FIG. 5 is schematic representation of the electrical connectors,according to the present invention;

FIG. 6 a is a top view showing the bump pads of the driver IC iselectrically connected to bump pads on the active area of a displaydevice;

FIG. 6 b is a cross sectional view showing the electric connectionbetween the driver IC and the active area;

FIG. 7 shows a finished LCD panel with the bump pad layout, according tothe present invention;

FIG. 8 shows the various dimensions in the bump-pad layout, according tothe present invention;

FIG. 9 shows another bump-pad layout, according to the presentinvention;

FIG. 10 shows a finished LCD panel with the other bump pad layout,according to the present invention;

FIG. 11 shows the detailed relationship between various strip segmentsand the bump pads, according to the present invention; and

FIG. 12 shows the electrical connection with a different bump pad.

FIG. 13 shows a different embodiment of the present invention where bothof the connected devices have a plurality of strip segments connected toa plurality of bump pads.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 5 shows the electrical connectors on the devices, according to thepresent invention. As shown, the connectors on the active area of adisplay device 200 include a plurality of conductive strip segments 532connected to a plurality of bump pads 530. The bump pads 530 are widerthan the strip segments 532. As shown in FIG. 5, the connectors on thedriver IC 220 include a plurality of bump pads 540 disposed on theunderside of the driver IC 220, complementary to the bump pads 530.

In connecting the connectors on the active area of the display device200 to the connectors on the driver IC 220, a bump pad 540 on the driverIC 220 is superimposed on a corresponding bump pad 530 on the activearea of the display device 200, and an electrically conductive medium,such as an anisotropic conductive film (ACF) 510 is provided between thebump pad 540 and the bump pad 530, as shown in FIG. 6 a and FIG. 6 b.FIG. 6 b shows that the electrically conductive medium 510 is providedbetween the active area of the driver IC 200 and the substrate. The bumppad 530, the strip segment 532 and the active area of the display device200 are typically fabricated on a glass substrate 500. The driver IC 220is mounted on the substrate via a COG process. As is known in the art,an ACF contains a plurality of electrically conductive particlessurrounded by a non-conductive medium. Normally, the ACF is notelectrically conductive. But when the ACF is pressed, the electricallyconductive particles become connected to each other to form a pluralityof conductive paths between its upper surface and its lower surface.

A finished display panel is shown in FIG. 7. As shown, the electricalconnections between the driver IC 230 and the active area of the displaydevice 200 have a connection pattern 550. Likewise, the electricalconnections between the IC 220 and the active area of the display device200 have a similar pattern. While the connection pattern 550 requiresmore area on the substrate 500, the closest distance W₂ between twoadjacent connectors is greater than the closest distance W₂ in the priorart layout.

In particular, the connected connectors are arranged in groups of threeconnectors, as shown in FIG. 8. As such, the relationship between thepitch, P, and other dimensions W₁, W₂ and W₃ is given below:P=(W ₁+3×W ₂+2×W ₃)/3.If we maintain the same dimensions in P, W₁ and W₃ as in the connectionpattern 350 as shown in FIG. 4, with P=21 μm, W₁=23 μm, and W₃=5 μm, wehaveW ₂=(3×P−W ₁−2×W ₃)/3=10 μm.Thus, with the same pitch, bump pad width and the strip segment width,the closest gap between two connectors is increased from 7 μm to 10 μmin this case. With such a connection pattern, the mechanical tolerancein superimposing the bump pads can be loosened. However, if the minimumgap W₂=7 is used, the pitch can be reduced from 21 μm to 18 μm, a 14%reduction. In other words, using the connection pattern 550, it ispossible to fabricate more lines on a given width of the substrate.

FIG. 9 shows a variation in connection pattern, according to the presentinvention. In the connection pattern 560, each group of connector is amirror image of an adjacent group. However, the relationship between thepitch, the width of the bump pad, the width of the strip segment and thegap between two adjacent connectors is the same.

FIG. 10 shows a finished LCD display 100′ with the connection pattern560.

It should be noted that, in general, the relationship between the pitch,P, and the other relevant dimensions is given by:P=(W ₁ +n×W ₂+(n−1)×W ₃)/n,where n is the number of connectors in a group of connectors. Accordingto the present invention, n is equal to or greater than 3. If we arrangethe connected connectors in groups of four, thenP=(W ₁+4×W ₂+3×W ₃)/4.With W₁=23 μm, W₂=7 μm and W₃=5 μm, we have P=16.5 μm. While it ispossible to fabricate more lines on a given width of the substrate, itrequires more area because of the increased length of the connectionpattern.

In sum, the present invention provides a method to improve electricalconnection layout efficiency in an electronic panel having a firstdevice and a second device, wherein the first device comprises aplurality of electrically conductive strip segments and a plurality offirst electrically conductive pads, and the second device comprises aplurality of second electrically conductive pads complementary to thefirst electrically conductive pads. As can be seen in FIG. 11, when thefirst pads are superimposed on corresponding second pads to form aplurality of pad stacks, the pad stacks together with the strip segmentsform a connection pattern between the first device and the seconddevice, wherein

each pad stack has an area bound by a first pad side and a second padside in a first direction, and by a first pad edge and a second pad edgein a second direction, and each of the first and second strip segmentshas a first strip edge and an opposing second strip edge, wherein eachpad stack is electrically connected to one strip segment on the firstpad side, and wherein

on each pad, the strip segments are arranged relative to the pad suchthat

the first strip edge of the second strip segment is substantiallyaligned with the first pad edge, and

the plurality of pad stacks in the connection pattern are arranged intoone or more groups, each group having at least three pad stacks,wherein, in each group, the pad stacks are displaced from each otherboth in the first direction and in the second direction such that

a gap is formed in the first direction between the second pad side ofone pad stack and the first pad side of an adjacent pad stack, and

a further gap is formed in the second direction between the second padedge of said pad stack and the first strip edge of the strip segmentconnected to said adjacent pad stack.

The groups in the connection pattern are arranged in a repetitivefashion such that each group is similar to the other groups.Alternatively, the groups in the connection pattern are arranged suchthat one group is the mirror image of an adjacent group.

It should also be appreciated that the bump pads do not have to beperfectly rectangular although a rectangular pad of a certain width anda certain length has the largest area. Nevertheless, the presentinvention is also applicable to bump pads of other shapes. For example,the bump pads can have one or more rounded corners, as shown in FIG. 12.

Furthermore, it is also possible that both the first device and thesecond device have a plurality of strip segments connected to aplurality of pads, with the strip segments and the pads of the seconddevice being complementary to the strip segments and the pads of thefirst device, as shown in FIG. 13.

Thus, although the present invention has been described and illustratedwith respect to exemplary embodiments thereof, the foregoing and variousother additions and omissions may be made therein without departing fromand scope of the present invention.

1. A method for use in an electronic panel having a first electronicdevice and a second electronic device, said method comprising: disposingon the first electronic device a plurality of electrically conductivestrip segments and a plurality of first electrically conductive pads;disposing on the second electronic device a plurality of secondelectrically conductive pads complementary to the first electricallyconductive pads, such that when the first pads are superimposed oncorresponding second pads to form a plurality of pad stacks, the padstacks together with the strip segments form a connection patternbetween the first electronic device and the second electronic device,wherein each pad stack has an area bound by a first pad side and asecond pad side in a first direction, and by a first pad edge and asecond pad edge in a second direction, and each of the strip segmentshas a first strip edge and an opposing second strip edge, each pad stackelectrically connected to one strip segment on the first pad side; andarranging the pad stacks in the connection pattern into a plurality ofstack groups, at least some of the stack groups having at least threepad stacks, wherein the second strip edge of the strip segment on eachpad stack in said at least some of the stack groups is substantiallyaligned with the second pad edge, and said at least three pad stacks aredisplaced from each other both in the first direction and in the seconddirection such that a gap is formed in the first direction between thesecond pad side of one pad stack and the first pad side of an adjacentpad stack, and a further gap is formed in the second direction betweenthe second pad edge of said pad stack and the first strip edge of thestrip segment connected to said adjacent pad stack.
 2. The method ofclaim 1, wherein said plurality of stack groups further comprises one ormore other stack groups, each of said other stack groups having at leastthree pad stacks, wherein the first strip edge of the strip segment oneach pad stack in said one or more other stack groups is substantiallyaligned with the first pad edge, and said at least three pad stacks aredisplaced from each other both in the first direction and in the seconddirection.
 3. The method of claim 2, wherein the stack groups and theother stack groups are arranged in an alternate pattern.
 4. The methodof claim 1, wherein the first electronic device comprises a liquidcrystal display having an active area, and wherein the plurality ofelectrically conductive strip segments are electrically connected to theactive area.
 5. The method of claim 4, wherein the second electronicdevice comprises a driver integrated circuit.
 6. The method of claim 4,wherein some of the plurality of electrically conductive strip segmentsare used to provide signals to gate lines in the liquid crystal display,and the second electronic device comprises a gate driver.
 7. The methodof claim 4, wherein some of the plurality of electrically conductivestrip segments are used to provide signals to data lines in the liquidcrystal display, and the second electronic device comprises a datadriver.
 8. An electronic panel comprising: a first electronic device; asecond electronic device; and an electrical connector electricallyconnecting the first electronic device to the second electronic device,said electrical connector comprising: a plurality of first electricallyconductive bump pads and a plurality of electrically conductive stripsegments connected between the first electrically conductive bump padsand the first electronic device; and a plurality of second electricallyconductive bump pads complementary to the first electrically conductivebump pads electrically connected to the second electronic device, suchthat when the first pads are superimposed on corresponding second padsto form a plurality of pad stacks, the pad stacks together with thestrip segments form a connection pattern between the first electronicdevice and the second electronic device, wherein each pad stack has anarea bound by a first pad side and a second pad side in a firstdirection, and by a first pad edge and a second pad edge in a seconddirection, and each of the strip segments has a first strip edge and anopposing second strip edge, each pad stack electrically connected to onestrip segment on the first pad side, and wherein the pad stacks in theconnection pattern are arranged into a plurality of stack groups, atleast some of the stack groups having at least three pad stacks, withthe second strip edge of the strip segment on each pad stack in said atleast some of the stack groups substantially aligned with the second padedge, and said at least three pad stacks are displaced from each otherboth in the first direction and in the second direction such that a gapis formed in the first direction between the second pad side of one padstack and the first pad side of an adjacent pad stack, and a further gapis formed in the second direction between the second pad edge of saidpad stack and the first strip edge of the strip segment connected tosaid adjacent pad stack.
 9. The electronic panel of claim 8, whereinsaid plurality of stack groups further comprises one or more other stackgroups, each of said other stack groups having at least three padstacks, wherein the first strip edge of the strip segment on each padstack in said one or more other stack groups is substantially alignedwith the first pad edge, and said at least three pad stacks aredisplaced from each other both in the first direction and in the seconddirection.
 10. The electronic panel of claim 9, wherein the stack groupsand the other stack groups are arranged in an alternate pattern.
 11. Theelectronic panel of claim 8, wherein the first electronic devicecomprises a liquid crystal display having an active area, and whereinthe plurality of electrically conductive strip segments are electricallyconnected to the active area.
 12. The electronic panel of claim 11,wherein the second electronic device comprises a driver integratedcircuit.
 13. The electronic panel of claim 11, wherein some of theplurality of electrically conductive strip segments are used to providesignals to gate lines in the liquid crystal display, and the secondelectronic device comprises a gate driver.
 14. The electronic panel ofclaim 11, wherein some of the plurality of electrically conductive stripsegments are used to provide signals to data lines in the liquid crystaldisplay, and the second electronic device comprises a data driver.